DSpace
 

DSpace at IIT Bombay >
IITB Publications >
Article >

Please use this identifier to cite or link to this item: http://dspace.library.iitb.ac.in/jspui/handle/10054/4460

Title: Spectroscopic studies on methyl torsional behavior in 1-methyl-2(1H)-pyridone, 1-methyl-2(1H)-pyridinimine, and 3-methyl-2(1H)-pyridone. I. Excited state
Authors: SINHA, RK
PRADHAN, B
WATEGAONKAR, S
SINGH, BP
KUNDU, T
Keywords: pi(asterisk)-sigma(asterisk) hyperconjugation mechanism
intramolecular vibrational redistribution
ethane internal-rotation
dipole-moment
microwave-spectrum
p-fluorotoluene
substituted toluenes
coupling constants
deuterated analog
flexing analysis
Issue Date: 2007
Publisher: AMER INST PHYSICS
Citation: JOURNAL OF CHEMICAL PHYSICS, 126(11), -
Abstract: The laser induced fluorescence excitation and dispersed fluorescence spectra of three nitrogen heterocyclic molecules 1-methyl-2(1H)pyridone (1MPY), 1-methyl-2(1H)pyridinimine (1MPI), and 3-methyl-2(1H)pyridone (3MPY) have been studied under supersonic jet cooled condition. The methyl torsional and some low frequency vibrational transitions in the fluorescence excitation spectrum were assigned for 1MPY. These new assignments modify the potential parameters to the methyl torsion reported earlier. Some striking similarities exist between the torsional and vibrational transitions in the fluorescence excitation spectra of 1MPY and 1MPI. Apart from pure torsional transitions, a progression of vibration-torsion combination bands was observed for both these molecules. The excitation spectrum of 3MPY resembles the spectrum of its parent molecule, 2-pyridone. The barrier height of the methyl torsion in the excited state of 3MPY is highest amongst all these molecules, whereas the barrier in 1MPI is higher than that of 1MPY. To get an insight into the methyl torsional barrier for these molecules, results of the ab initio calculations were compared with the experimental results. It was found that the conformation of the methyl group undergoes a 60 degrees rotation in the excited state in all these molecules with respect to their ground state conformation. This phase shift of the excited state potential is attributed to the pi(*)-sigma(*) hyperconjugation between the out-of-plane hydrogen of the methyl group and the molecular frame. It has been inferred that the change in lowest unoccupied molecular orbital energy plays the dominant role in the excited state barrier formation.
URI: http://dx.doi.org/10.1063/1.2566574
http://dspace.library.iitb.ac.in/xmlui/handle/10054/4460
http://hdl.handle.net/10054/4460
ISSN: 0021-9606
Appears in Collections:Article

Files in This Item:

File SizeFormat
117.pdf981.76 kBAdobe PDFView/Open
View Statistics

Items in DSpace are protected by copyright, with all rights reserved, unless otherwise indicated.

 

Valid XHTML 1.0! DSpace Software Copyright © 2002-2010  Duraspace - Feedback